Question: $rs + 2rt - r - 5 = -4s - 1$ Solve for $r$.
Solution: Combine constant terms on the right. $rs + 2rt - r - {5} = -4s - {1}$ $rs + 2rt - r = -4s + {4}$ Notice that all the terms on the left-hand side of the equation have $r$ in them. $1{r}s + 2{r}t - 1{r} = -4s + 4$ Factor out the $r$ ${r} \cdot \left( s + 2t - 1 \right) = -4s + 4$ Isolate the $r$ $r \cdot \left( {s + 2t - 1} \right) = -4s + 4$ $r = \dfrac{ -4s + 4 }{ {s + 2t - 1} }$